Pass agent logs to monitor after package B&R

In this change B&R tasks ask for logs from each BackupAgent after it is
backed up or restored. These logs are then immediately passed on to the
BackupManagerMonitor.

Bug: 252760247
Change-Id: Iaf43ce61e98bb4b42c05c18a46031a06d41abb12
Test: $ atest BackupFrameworksServicesRoboTests:KeyValueBackupTaskTest
  $ atest BackupManagerMonitorUtilsTest
  Unfortunately, the other classes are not unit testable.
  For manual testing, I implemented some fake loggers for various
  BackupAgents, passed in a fake BackupManagerMonitor, ran B&R with the
  following commands, and observed that the monitor received the logs.
  1. $ adb shell bmgr backupnow --all
  2. $ adb shell bmgr restore ... (for one KV and one FullBackup package)